Conventionally, to manage a large-scale network system, a technique to hierarchize an operation management manager, which is an operation management apparatus, has been used. As an example of such a large-scale system environment management, there is an operation management of a distributed computer system in a large-scale data center or the like. Various techniques for monitoring whether a node is dead or alive on a network are known.    Patent Document 1: Japanese Laid-open Patent Publication No. 11-85649    Patent Document 2: Japanese Laid-open Patent Publication No. 2009-77216
When performing operation management of a network of a large-scale data center or the like by hierarchizing an operation management manager, for example, LinkUp and LinkDown events by polling and SNMP (Simple Network Management Protocol) Trap are sequentially transmitted to managers in each hierarchy. Therefore, there is a problem that a time lag occurs in detecting the LinkUp and LinkDown events. Further, CPU (Central Processing Unit) utilization of the managers and network traffic increase due to periodic polling from the managers to objects to be managed.